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   1 /*
   2  * linux/kernel/itimer.c
   3  *
   4  * Copyright (C) 1992 Darren Senn
   5  */
   6
   7 /* These are all the functions necessary to implement itimers */
   8
   9 #include <linux/mm.h>
  10 #include <linux/interrupt.h>
  11 #include <linux/syscalls.h>
  12 #include <linux/time.h>
  13 #include <linux/posix-timers.h>
  14 #include <linux/hrtimer.h>
  15
  16 #include <asm/uaccess.h>
  17
  18 /**
  19  * itimer_get_remtime - get remaining time for the timer
  20  *
  21  * @timer: the timer to read
  22  *
  23  * Returns the delta between the expiry time and now, which can be
  24  * less than zero or 1usec for an pending expired timer
  25  */
  26 static struct timeval itimer_get_remtime(struct hrtimer *timer)
  27 {
  28         ktime_t rem = hrtimer_get_remaining(timer);
  29
  30         /*
  31          * Racy but safe: if the itimer expires after the above
  32          * hrtimer_get_remtime() call but before this condition
  33          * then we return 0 - which is correct.
  34          */
  35         if (hrtimer_active(timer)) {
  36                 if (rem.tv64 <= 0)
  37                         rem.tv64 = NSEC_PER_USEC;
  38         } else
  39                 rem.tv64 = 0;
  40
  41         return ktime_to_timeval(rem);
  42 }
  43
  44 int do_getitimer(int which, struct itimerval *value)
  45 {
  46         struct task_struct *tsk = current;
  47         cputime_t cinterval, cval;
  48
  49         switch (which) {
  50         case ITIMER_REAL:
  51                 spin_lock_irq(&tsk->sighand->siglock);
  52                 value->it_value = itimer_get_remtime(&tsk->signal->real_timer);
  53                 value->it_interval =
  54                         ktime_to_timeval(tsk->signal->it_real_incr);
  55                 spin_unlock_irq(&tsk->sighand->siglock);
  56                 break;
  57         case ITIMER_VIRTUAL:
  58                 read_lock(&tasklist_lock);
  59                 spin_lock_irq(&tsk->sighand->siglock);
  60                 cval = tsk->signal->it_virt_expires;
  61                 cinterval = tsk->signal->it_virt_incr;
  62                 if (!cputime_eq(cval, cputime_zero)) {
  63                         struct task_struct *t = tsk;
  64                         cputime_t utime = tsk->signal->utime;
  65                         do {
  66                                 utime = cputime_add(utime, t->utime);
  67                                 t = next_thread(t);
  68                         } while (t != tsk);
  69                         if (cputime_le(cval, utime)) { /* about to fire */
  70                                 cval = jiffies_to_cputime(1);
  71                         } else {
  72                                 cval = cputime_sub(cval, utime);
  73                         }
  74                 }
  75                 spin_unlock_irq(&tsk->sighand->siglock);
  76                 read_unlock(&tasklist_lock);
  77                 cputime_to_timeval(cval, &value->it_value);
  78                 cputime_to_timeval(cinterval, &value->it_interval);
  79                 break;
  80         case ITIMER_PROF:
  81                 read_lock(&tasklist_lock);
  82                 spin_lock_irq(&tsk->sighand->siglock);
  83                 cval = tsk->signal->it_prof_expires;
  84                 cinterval = tsk->signal->it_prof_incr;
  85                 if (!cputime_eq(cval, cputime_zero)) {
  86                         struct task_struct *t = tsk;
  87                         cputime_t ptime = cputime_add(tsk->signal->utime,
  88                                                       tsk->signal->stime);
  89                         do {
  90                                 ptime = cputime_add(ptime,
  91                                                     cputime_add(t->utime,
  92                                                                 t->stime));
  93                                 t = next_thread(t);
  94                         } while (t != tsk);
  95                         if (cputime_le(cval, ptime)) { /* about to fire */
  96                                 cval = jiffies_to_cputime(1);
  97                         } else {
  98                                 cval = cputime_sub(cval, ptime);
  99                         }
 100                 }
 101                 spin_unlock_irq(&tsk->sighand->siglock);
 102                 read_unlock(&tasklist_lock);
 103                 cputime_to_timeval(cval, &value->it_value);
 104                 cputime_to_timeval(cinterval, &value->it_interval);
 105                 break;
 106         default:
 107                 return(-EINVAL);
 108         }
 109         return 0;
 110 }
 111
 112 asmlinkage long sys_getitimer(int which, struct itimerval __user *value)
 113 {
 114         int error = -EFAULT;
 115         struct itimerval get_buffer;
 116
 117         if (value) {
 118                 error = do_getitimer(which, &get_buffer);
 119                 if (!error &&
 120                     copy_to_user(value, &get_buffer, sizeof(get_buffer)))
 121                         error = -EFAULT;
 122         }
 123         return error;
 124 }
 125
 126
 127 /*
 128  * The timer is automagically restarted, when interval != 0
 129  */
 130 enum hrtimer_restart it_real_fn(struct hrtimer *timer)
 131 {
 132         struct signal_struct *sig =
 133             container_of(timer, struct signal_struct, real_timer);
 134
 135         send_group_sig_info(SIGALRM, SEND_SIG_PRIV, sig->tsk);
 136
 137         return HRTIMER_NORESTART;
 138 }
 139
 140 /*
 141  * We do not care about correctness. We just sanitize the values so
 142  * the ktime_t operations which expect normalized values do not
 143  * break. This converts negative values to long timeouts similar to
 144  * the code in kernel versions < 2.6.16
 145  *
 146  * Print a limited number of warning messages when an invalid timeval
 147  * is detected.
 148  */
 149 static void fixup_timeval(struct timeval *tv, int interval)
 150 {
 151         static int warnlimit = 10;
 152         unsigned long tmp;
 153
 154         if (warnlimit > 0) {
 155                 warnlimit--;
 156                 printk(KERN_WARNING
 157                        "setitimer: %s (pid = %d) provided "
 158                        "invalid timeval %s: tv_sec = %ld tv_usec = %ld\n",
 159                        current->comm, current->pid,
 160                        interval ? "it_interval" : "it_value",
 161                        tv->tv_sec, (long) tv->tv_usec);
 162         }
 163
 164         tmp = tv->tv_usec;
 165         if (tmp >= USEC_PER_SEC) {
 166                 tv->tv_usec = tmp % USEC_PER_SEC;
 167                 tv->tv_sec += tmp / USEC_PER_SEC;
 168         }
 169
 170         tmp = tv->tv_sec;
 171         if (tmp > LONG_MAX)
 172                 tv->tv_sec = LONG_MAX;
 173 }
 174
 175 /*
 176  * Returns true if the timeval is in canonical form
 177  */
 178 #define timeval_valid(t) \
 179         (((t)->tv_sec >= 0) && (((unsigned long) (t)->tv_usec) < USEC_PER_SEC))
 180
 181 /*
 182  * Check for invalid timevals, sanitize them and print a limited
 183  * number of warnings.
 184  */
 185 static void check_itimerval(struct itimerval *value) {
 186
 187         if (unlikely(!timeval_valid(&value->it_value)))
 188                 fixup_timeval(&value->it_value, 0);
 189
 190         if (unlikely(!timeval_valid(&value->it_interval)))
 191                 fixup_timeval(&value->it_interval, 1);
 192 }
 193
 194 int do_setitimer(int which, struct itimerval *value, struct itimerval *ovalue)
 195 {
 196         struct task_struct *tsk = current;
 197         struct hrtimer *timer;
 198         ktime_t expires;
 199         cputime_t cval, cinterval, nval, ninterval;
 200
 201         /*
 202          * Validate the timevals in value.
 203          *
 204          * Note: Although the spec requires that invalid values shall
 205          * return -EINVAL, we just fixup the value and print a limited
 206          * number of warnings in order not to break users of this
 207          * historical misfeature.
 208          *
 209          * Scheduled for replacement in March 2007
 210          */
 211         check_itimerval(value);
 212
 213         switch (which) {
 214         case ITIMER_REAL:
 215 again:
 216                 spin_lock_irq(&tsk->sighand->siglock);
 217                 timer = &tsk->signal->real_timer;
 218                 if (ovalue) {
 219                         ovalue->it_value = itimer_get_remtime(timer);
 220                         ovalue->it_interval
 221                                 = ktime_to_timeval(tsk->signal->it_real_incr);
 222                 }
 223                 /* We are sharing ->siglock with it_real_fn() */
 224                 if (hrtimer_try_to_cancel(timer) < 0) {
 225                         spin_unlock_irq(&tsk->sighand->siglock);
 226                         goto again;
 227                 }
 228                 expires = timeval_to_ktime(value->it_value);
 229                 if (expires.tv64 != 0) {
 230                         tsk->signal->it_real_incr =
 231                                 timeval_to_ktime(value->it_interval);
 232                         hrtimer_start(timer, expires, HRTIMER_MODE_REL);
 233                 } else
 234                         tsk->signal->it_real_incr.tv64 = 0;
 235
 236                 spin_unlock_irq(&tsk->sighand->siglock);
 237                 break;
 238         case ITIMER_VIRTUAL:
 239                 nval = timeval_to_cputime(&value->it_value);
 240                 ninterval = timeval_to_cputime(&value->it_interval);
 241                 read_lock(&tasklist_lock);
 242                 spin_lock_irq(&tsk->sighand->siglock);
 243                 cval = tsk->signal->it_virt_expires;
 244                 cinterval = tsk->signal->it_virt_incr;
 245                 if (!cputime_eq(cval, cputime_zero) ||
 246                     !cputime_eq(nval, cputime_zero)) {
 247                         if (cputime_gt(nval, cputime_zero))
 248                                 nval = cputime_add(nval,
 249                                                    jiffies_to_cputime(1));
 250                         set_process_cpu_timer(tsk, CPUCLOCK_VIRT,
 251                                               &nval, &cval);
 252                 }
 253                 tsk->signal->it_virt_expires = nval;
 254                 tsk->signal->it_virt_incr = ninterval;
 255                 spin_unlock_irq(&tsk->sighand->siglock);
 256                 read_unlock(&tasklist_lock);
 257                 if (ovalue) {
 258                         cputime_to_timeval(cval, &ovalue->it_value);
 259                         cputime_to_timeval(cinterval, &ovalue->it_interval);
 260                 }
 261                 break;
 262         case ITIMER_PROF:
 263                 nval = timeval_to_cputime(&value->it_value);
 264                 ninterval = timeval_to_cputime(&value->it_interval);
 265                 read_lock(&tasklist_lock);
 266                 spin_lock_irq(&tsk->sighand->siglock);
 267                 cval = tsk->signal->it_prof_expires;
 268                 cinterval = tsk->signal->it_prof_incr;
 269                 if (!cputime_eq(cval, cputime_zero) ||
 270                     !cputime_eq(nval, cputime_zero)) {
 271                         if (cputime_gt(nval, cputime_zero))
 272                                 nval = cputime_add(nval,
 273                                                    jiffies_to_cputime(1));
 274                         set_process_cpu_timer(tsk, CPUCLOCK_PROF,
 275                                               &nval, &cval);
 276                 }
 277                 tsk->signal->it_prof_expires = nval;
 278                 tsk->signal->it_prof_incr = ninterval;
 279                 spin_unlock_irq(&tsk->sighand->siglock);
 280                 read_unlock(&tasklist_lock);
 281                 if (ovalue) {
 282                         cputime_to_timeval(cval, &ovalue->it_value);
 283                         cputime_to_timeval(cinterval, &ovalue->it_interval);
 284                 }
 285                 break;
 286         default:
 287                 return -EINVAL;
 288         }
 289         return 0;
 290 }
 291
 292 /**
 293  * alarm_setitimer - set alarm in seconds
 294  *
 295  * @seconds:    number of seconds until alarm
 296  *              0 disables the alarm
 297  *
 298  * Returns the remaining time in seconds of a pending timer or 0 when
 299  * the timer is not active.
 300  *
 301  * On 32 bit machines the seconds value is limited to (INT_MAX/2) to avoid
 302  * negative timeval settings which would cause immediate expiry.
 303  */
 304 unsigned int alarm_setitimer(unsigned int seconds)
 305 {
 306         struct itimerval it_new, it_old;
 307
 308 #if BITS_PER_LONG < 64
 309         if (seconds > INT_MAX)
 310                 seconds = INT_MAX;
 311 #endif
 312         it_new.it_value.tv_sec = seconds;
 313         it_new.it_value.tv_usec = 0;
 314         it_new.it_interval.tv_sec = it_new.it_interval.tv_usec = 0;
 315
 316         do_setitimer(ITIMER_REAL, &it_new, &it_old);
 317
 318         /*
 319          * We can't return 0 if we have an alarm pending ...  And we'd
 320          * better return too much than too little anyway
 321          */
 322         if ((!it_old.it_value.tv_sec && it_old.it_value.tv_usec) ||
 323               it_old.it_value.tv_usec >= 500000)
 324                 it_old.it_value.tv_sec++;
 325
 326         return it_old.it_value.tv_sec;
 327 }
 328
 329 asmlinkage long sys_setitimer(int which,
 330                               struct itimerval __user *value,
 331                               struct itimerval __user *ovalue)
 332 {
 333         struct itimerval set_buffer, get_buffer;
 334         int error;
 335
 336         if (value) {
 337                 if(copy_from_user(&set_buffer, value, sizeof(set_buffer)))
 338                         return -EFAULT;
 339         } else
 340                 memset((char *) &set_buffer, 0, sizeof(set_buffer));
 341
 342         error = do_setitimer(which, &set_buffer, ovalue ? &get_buffer : NULL);
 343         if (error || !ovalue)
 344                 return error;
 345
 346         if (copy_to_user(ovalue, &get_buffer, sizeof(get_buffer)))
 347                 return -EFAULT;
 348         return 0;
 349 }